Calling all floor pan replacement experts

BPBP440 · Jul 10, 2016

I am enjoying the challenge of a full floor pan replace in my 70 b-body.

Working my way up to the firewall flange during removal today and it is a bit intimidating. Any advice on tackling the floor pan to firewall interface? Looks a whole lot easier to cut the pan about 4-6" shy of the flange and overlap there with the new pan. But maybe I am making this harder than it really is.

poly3521 · Jul 10, 2016

I drilled the spot weld with a spotweld cutter and used a body chisel. Should pop out fairly easy as the firewall will flex just enough. The pain is getting the floor out of the car, get a few friends to help maneuver the it up and out.

SgtLee511 · Jul 11, 2016

I agree with Poly. I am working from the front to the back 69 my 69 RR. Drill the spot welds at the firewall, try not to use the air chisel, in my case it tore more than I wanted, but I did use it some. When you get to the drivers side its a little more difficult, there are some brackets on the frame rail to deal with, and I had the front fenders off. Don't forget to use weld thru primer. Heres some pics, still looking for my completed pics.

threewood · Jul 11, 2016

I am in the middle of a drivers side replace only so have no advice for a full replace. The firewall flange is easy to access from outside. Find and drill the spotwelds out. On mine, along the tunnel area, there were some welds that I popped with an easy hit with my air chisel. Chisel toward the bad metal with light and short raps. There are two splash shields, left and right, between the rail and rocker. Make sure to find and drill the 2 or 3 spotwelds in them.

5wndwcpe · Jul 11, 2016

These help

http://www.autobodytoolmart.com/steck-right-angle-seam-buster-20016-p-14255.aspx

http://www.autobodytoolmart.com/steck-seam-buster-20015-p-11711.aspx

747mopar · Jul 11, 2016

The way I like to do them is lay the new one on top of the old, screw it down tight, trace around the replacement (if using the whole panel) then remove it and trim the old floor leaving at least an inch overlap. Once the old is out I fasten the replacement floor back down and cut threw both layers at once with a 1/16 cutoff wheel. I do about 6" at a time tacking the trimmed panels as I go for a flush butt weld. The 1/16 gap allows you to get a full weld so it can be ground smooth. Always jump around with the tacks to avoid warping.

YY1 · Jul 11, 2016

I've got an OEM donor floor to cut out of one car and weld into another.

Never done anything that big.

I'm seriously considering what was posted above as it eliminates spot weld busting, that dang odd angle on the front seam, and messing with seam sealer.

funknut · Sep 27, 2019

SgtLee511 said:
I agree with Poly. I am working from the front to the back 69 my 69 RR. Drill the spot welds at the firewall, try not to use the air chisel, in my case it tore more than I wanted, but I did use it some. When you get to the drivers side its a little more difficult, there are some brackets on the frame rail to deal with, and I had the front fenders off. Don't forget to use weld thru primer. Heres some pics, still looking for my completed pics.

I'm in the middle of a full floor replacement and wanted to say thanks, these pics are incredibly helpful for me.

My car took a hit some time back and while the rockers and rails are square, the firewall is apparently tweaked. Good pics of original metal are a lifesaver. :thumbsup:

In your 2nd pic I see a dimple in the firewall on the outboard driver's side, but I don't see a matching dimple on the replacement floor, is this correct? I've circled it in red. My floor was rotten there so I don't have any good pics of the original.

Thanks in advance!

Coronet R/T 68 · Sep 27, 2019

I believe to do it right then you have to remove the entire floor and not do the overlap option. No disrespect to anyone that does, it's just my preference. I cut mine about 1/4 from the firewall seam and ground the spot weld down to the point I could pop the spot welds. I drilled holes in the firewall flange and plug welded the new floor pan. Learning from my trials, I would recommend going around all the flanges on the frames and torsion bar mount and look for low spots and tap them up before you put the floor in as it is nearly impossible to push the floor down to close any gaps that there might be from low spot from factory spot welds.

matthon · Sep 27, 2019

Cut it close, grind spotwelds off.

https://www.forbbodiesonly.com/mopa...replacement-front-seam.179881/#post-911368884

Crackedback · Sep 28, 2019

Realize this is an old thread and agree 100% with @matthon

If you are throwing away the entire old pan, cut off the old material close to the spot welded area and grind it off. Will be much more time friendly. Once out, drill holes in the firewall flange. Got a nice clean, not bent up from hammering spots apart surface to work back to the new pan lip.

I use this approach on anything I'm replacing. Trunk pans, screw the spot weld cutter, grind those suckers out with a flap wheel.

flypaper · Sep 28, 2019

if you aren't saving it, cut away the bulk
always makes it much easy to dig apart.
I would rather drill and bang it apart myself
because
I get sick of making a bunch of noise while grinding
if you are saving it, is when it takes some finesse, patience and thought
and then you won't be doing any grinding either.
overlapping is just a short cut
as you can get any full panel apart with a little time and effort.
wish I had a dollar every time I see 80% of a trunk floor removed
with a splice 4 inches before the top seam..lol

Calling all floor pan replacement experts

BPBP440

Well-Known Member

poly3521

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SgtLee511

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threewood

FBBO Gold Member

5wndwcpe

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747mopar

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YY1

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funknut

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Coronet R/T 68

Active Member

matthon

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Crackedback

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flypaper

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